Introduced around 1983-84, the TPA-11/440 was called a "megamini". It
was an enhancement to the DEC PDP-11 architecture. Some of the performance
improvements came from the greatly extended instruction set: it had 46
new standard floating-point instructions, and CIS/EIS as an option.

It also had a special 32-bit system bus, called the x-bus. Unfortunately
not many options used this new bus, most of the peripherals and other devices
were using the UBUS (the KFKI-equivalent of the UNIBUS), so there wasn't
really much on the x-bus besides the four-board CPU and the maximal
4MB memory (and of course the xbus-ubus converter). The performance
of the machine measured around 0.5-0.6 VUPs (VAX unit of performance).